1. Field of the Invention
This invention generally relates to the interfacing of electrical and optical communication signals and, more particularly, to a free space self-aligned optical connector and associated alignment method.
2. Description of the Related Art
Conventionally, communication signals are carried via conductive metal lines on a circuit board or metal wires in a connector cable. Copper and aluminum are metals often used for this purpose. With the increased use of high-speed long distance communications, optical signals were introduced, carried through an optical fiber medium. In some communication links, an interface must be used to convert between electrical and optical signals.
An electrical system such as a computer or communications network is comprised of a plurality of modules that are connected via cables. The cables are bulky and prone to failure. Optical cables are relatively stiff and difficult to fit into limited cabinet space or “bend” around corners.
A small form-factor pluggable (SFP) is a compact, hot-pluggable transceiver used in optical communications. It interfaces a network device mother board, such as a switch, router, or media converter, to a fiber optic or copper networking cable. It is a popular industry format supported by several network component vendors. SFP transceivers are designed to support SONET, Gigabit Ethernet, Fibre Channel, and other communications standards. The standard is expanding to SFP+, which will be able to support data rates up to 10.0 Gbit/s (e.g., 8 gigabit Fibre Channel and 10 GbE). SFP+ module versions for optics as well as copper are being introduced.
SFP transceivers are available with a variety of different transmitter and receiver types, allowing users to select the appropriate transceiver for each link, to provide the required optical reach over the available optical fiber type (e.g., multi-mode fiber or single-mode fiber). Optical SFP modules are commonly available in several different categories: 850 nm 550 m MMF (SX), 1310 nm 10 km SMF (LX), 1550 nm [40 km (XD), 80 km (ZX), 120 km (EX or EZX)], and DWDM. There are also CWDM and single-fiber “bi-directional” (1310/1490 nm Upstream/Downstream) SFPs. The SFP was designed after the GBIC interface, and allows for greater port density (number of transceivers per inch along the edge of a mother board) than the GBIC, which is why SFP is also known as mini-GBIC.
It is also possible to communicate optical signals via free space. The conventional television remote control uses infrared optical wavelengths to communicate commands. However, the optical signals are not focused, and can only be used to carry very simple communications a very short distance. The unfocused nature of the communications and the portable nature of the remote control unit prevent it from being used as a receiver, i.e. to receive signals from a television or set-top box.
It would be advantageous if optical signals could be communicated between circuit boards via free space, without the use of fiber optic cables. An optical signal can transport data over longer distances and with fewer errors if the signal paths between transmitter and receiver can be aligned, permitting in turn, the light source to be more tightly focused. However, due to manufacturing tolerances, “play” in the connectors, mechanically disruptive events, and temperature variations, such an optical link would likely require tedious and frequent realignment.
It would be advantageous if a self-alignment system existed for optical signals communicated between circuit boards via free space, to support uninterrupted communication.